The common way to to have a beacon at the base that the robot can detect and determine the direction to. Then the robot moves to the beacon.

Modulated IR light has been used most successfully but the robot must have 'line of sight' to the beacon. RF (radio) has also been used but the biggest difficultly is for the robot to determine the direction to the RF source.

what about checkpoints throughout your house or wherever?so the robot must not have a line of sight to the base, just a checkpoint, once at the checkpoint it will have a line of sight to the next checkpoint/base?